JPS63249627A - Manufacture of releasable material - Google Patents

Abstract

PURPOSE:To improve the release performance of a material by a method wherein polyolefin-based thermoplastic resin is blended with dimethyl polysiloxane and, after that, molded and finally subjected to a treatment of radiation of electron rays. CONSTITUTION:A composition consisting of polyolefin-based thermoplastic resin and dimethyl polysiloxane is molded, and the dimethyl polysiloxane is bleeded on the surface of a molded item. After that, electron rays are irradiated over the molded item. In addition, the molded item is heat-treated in the air at a temperature below the melting point of the polyolefin-based thermoplastic resin. To 100 parts by weight of polyolefin-based thermoplastic resin, 0.5-30 parts by weight, preferably 1-15 parts by weight and most preferably 2-6 parts by weight of the dimethyl polysiloxane is blended. The exposed dose of electron ray can be changed in wide range in response to the required performance of a matter to be irradiated. The dose is normally less than or equal to 20 Mrad, preferably 2-10 Mrad, most preferably 3-8 Mrad.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention mainly relates to a method for manufacturing release paper, etc. that imparts releasability to the base surface of patches, stickers, etc., or the back surface of wound packaging tape, etc. .

[Conventional technology]

Conventionally, release paper used as a base for adhesive sheets such as straw, stickers, etc., or the back side of wound packaging adhesive tapes, etc., has a polyolefin-laminated base in order to exhibit releasability. Previously, expensive reactive silicone was applied onto the surface of the material, followed by a heat curing process.The process consisted of applying the silicone, drying it, and crosslinking it.

Usually, the length of the equipment at that time reaches several tens of meters, making it large-scale. Furthermore, since a solvent such as toluene is used when applying reactive silicone, a large amount of equipment cost and energy is required to recover the solvent.

[Problem that the invention seeks to solve]

If a release paper with good performance can be produced by mixing the silicone oil with a thermoplastic resin, the large-scale process described above can be omitted.

However, in this case, the releasability required for release paper is not achieved, and the silicone oil that bleeds onto the surface transfers to the adhesive layer of patches, stickers, etc., reducing its adhesive strength. This is a fatal flaw as a seal.

As a method to solve this problem,
No. 21 proposes a method in which a radiation-curable organopolysiloxane is added and mixed with a resin, molded by lamination and inflation methods, and then irradiated with radiation. If siloxane is not used, practical performance will not be achieved.

[Means for solving problems]

The inventors of the present invention took into consideration the problems with the current methods described above, and as a result of intensive studies to develop an inexpensive method for producing removable materials that does not require complicated processes, the inventors found that they A composition consisting of a chemically stable dimethylpolysiloxane and a polyolefin thermoplastic resin, which is difficult to cure by simply heating, is molded, and after the dimethylpolysiloxane bleeds onto the surface of the molded product, it is irradiated with an electron beam. It was found that excellent peeling performance (low peel strength and high residual adhesion rate) was achieved by applying this method, and more surprisingly, despite the high peeling performance, the marker ink writing properties were good. Discover.

This is proposed as a new method for producing release paper.

After further intensive research, the present researchers found that after electron beam irradiation, heat treatment in air at a temperature below the melting point of the polyolefin thermoplastic resin further improved the peeling performance and the irradiation dose. It has been discovered that good peeling performance can be achieved even when the

The present invention was made based on the discovery that dimethylpolysiloxane, which had extremely low reactivity and was difficult to exhibit its performance, could be used as a stripping agent.

[Specific structure and operation of the invention]

The present invention will be explained in detail below.

The polyolefin thermoplastic resin used as a raw material in the present invention includes high-density teriethylene, medium-density polyethylene, and low-density polyethylene.

Polypropylene and copolymers thereof, copolymers of ethylene and vinyl esters or α,β-unsaturated carboxylic acid esters, etc. can be used. Preferably, ethylene polymer, ethylene-propylene copolymer, ethylene-butene copolymer, polypropylene, polybutene, poly-4
-Methyl-1-pentene can be used. These can exhibit performance even when used alone, but performance can be facilitated by using a mixture of two or more specific types.

In this case, it is preferable to use a mixture containing polyethylene and a homopolymer or copolymer of C3 to C5 α-olefin as essential components. Among these, it is suitable to use a mixture of low density polyethylene and polypropylene. Its composition ratio is 1. j51J Polypropylene 99 to 1 weight percent to 1 to 99 weight i% of polyethylene, preferably,
90% by weight or less to 60% by weight of polypropylene to 10% by weight or more to 40% by weight of polyethylene
Above, polypropylene is 10% to 40% by weight, more preferably polyethylene 15% to 40% by weight, based on 90% to 60% by weight of polyethylene.
785-70% by weight of polyglo tv to 30% by weight and 15-30% by weight of polypropylene to 85-70% by weight of polyethylene. Polyethylene is more than 40% by weight (polypropylene is less than 60% by weight)
If the amount is more than 40% by weight, there will be no problem in terms of performance, but the moldability will be significantly worse.

The mea/) index or melt 20-index of polyolefin thermoplastic resin is generally 0.01.
~200.9/l0m1n), 0.1~10010
0l710 is desirable, and 1 to 20.9/lomin is suitable.

Furthermore, the melt index of a mixture of low density polyethylene and polypropylene, which is the composition that most easily exhibits performance, is 0. Ol ~20
0 g/10m1n, and O,l ~l OOg/1
0m1n is desirable, 0.5~15,! i'/1or
nin is preferred, polypropylene and siteha, 0. O
1~150,! i'/lomin, l-100,
S'/10m1n is desirable.

2 to 30.9/l 0 m1n is suitable.

In addition, the dimethylpolysiloxane to be mixed with the polyolefin thermoplastic resin has a terminal of 18iR1R2R3.
(However, R', R2, and R' are each independently selected from a methyl group, a hydroxyl group, and a C1 to C3 flukoxy group.) Difficult to mix with dimethylpolysiloxane-based thermoplastic resin and difficult to mold. In order to exhibit sufficient peeling performance without being fragile, a large irradiation dose is required, which significantly reduces the mechanical strength of the matrix resin. Moreover, if it exceeds 8XIO'C8, it becomes difficult to exhibit sufficient peeling performance.

In addition, the mixing ratio of dimethylpolysiloxane with the polyoxydiyne thermoplastic resin is 0.5 to 30% by weight, and 1 to 15% by weight with respect to the polyolefin thermoplastic resin.
is preferable, and 2 to 6% by weight is suitable. The amount is 0.
If it is less than 5% by weight, sufficient peeling performance cannot be obtained, and if it exceeds 30% by weight, dimethylpolysiloxane cannot be mixed.
However, it is either very difficult to mold or disadvantageous in terms of cost.

In order to mix the above polyolefin thermoplastic resin and dimethylpolysiloxane, it is generally necessary to cross-wire the synthetic resin,
Equipment used for mixing can be used. For example, Banbury mixer, kneader 1 twin screw extruder, single screw extruder,
There is a method of melting and mixing using a mixer such as a roll mill. In particular, when dimethylpolysiloxane having a low viscosity is used, ordinary mixing becomes difficult, so dimethylpolysiloxane is injected into the middle of the cylinder of the extruder to mix it.

In order to mold the above mixture, the usual extrusion lamination method, coextrusion lamination method, inflation method, coextrusion di-inflation method is used for the following purposes:
It may be selected as appropriate depending on the purpose. By subjecting this molded product to electron beam irradiation treatment, a releasable surface can be formed. It varies depending on the viscosity of siloxane and the addition tK of dimethylpolysiloxane. In many cases, it bleeds completely immediately after molding, but it can be aged if necessary. When aging, the temperature may be applied to a degree that does not cause deformation, or it may be at room temperature. In relation to dimethylpolysiloxane, those with lower viscosity are more advantageous.

Methods for carrying out the above electron beam treatment include Kotsukucroft type, Kotskucroft Walton type, bumpgraph type,
Examples include methods of emitting electron beams from various types of electron beam accelerators, such as insulated core transformer type, linear type, dynamidron type, high frequency type, and electron curtain type. The irradiation dose can vary within a wide range depending on the required performance of the irradiated object. In general, it is less than 20 megarads, and 2 to
A value of 10 megarads is desirable, and a range of 3 to 8 megarads is preferred. If the irradiation dose exceeds 20 megarads, the mechanical strength of the matrix will be weak, making it impractical. Also, the acceleration voltage is not particularly particular, but it is 100 to 30
0 kV is practical.

The atmosphere during irradiation is basically an inert gas atmosphere. However, in the case of polyethylene.

It does not matter if it is in an oxygen atmosphere. In the case of α-olefins or C3 or higher monopolymers or copolymers, irradiation in an oxygen atmosphere causes significant deterioration and decreases in mechanical strength.

Heat treatment methods include a method of leaving the irradiated roll in a circulating type, a method of leaving it in a roll after irradiation, a method of passing it through a heated roll, and a method of passing it through a heated roll. It is desirable to leave the roll in place during the circulation and stationary openings.

Further, the temperature of the heat treatment is generally lower than the melting point of the polyolefin thermoplastic resin, but it varies depending on the type of polyolefin thermoplastic resin.

Generally, a temperature as high as possible below the melting point is preferred, but a temperature 5 to 10°C lower than the melting point is desirable.

Furthermore, the heat treatment time varies depending on the amount of silicone added and mixed, the composition of the resin, and the irradiation dose, but should be determined mainly in correlation with the heat treatment temperature. From the standpoint of performance, it does not matter how long the length is, but depending on the type of resin, if it is too long, the mechanical properties may deteriorate. In general, the period is from a few seconds to one week, preferably from 10 seconds to 3 days. Not clear. However, when a thermoplastic polyolefin resin that has the property of crosslinking or decomposing with electron beams coexists with dimethylpolysiloxane, the radicals generated in the polyolefin and the dimethylpolysiloxane radicals interact delicately and complexly, resulting in graft reactions and/or Alternatively, it is thought that it promotes crosslinking between siloxanes, leading to special performance. Through subsequent heat treatment,
This may have further accelerated the reaction that could not be completed by EB irradiation.

The method of the present invention eliminates the conventional large-scale coating and drying process.

Adjustment of peeling performance by changing and combining the mixing ratio of dimethylpolysiloxane used, resin composition, electron beam treatment conditions, heat treatment conditions, etc. without requiring a crosslinking step or a solvent recovery step. I can do it.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples; however, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

In Examples and Comparative Examples, the peel strength and residual adhesion of samples prepared under various conditions were measured, and the results are summarized in Table 1.

The peel strength and residual adhesion rate described above were measured as follows. That is, using Pylon Craft Cheve (manufactured by Kyowa Co., Ltd.) as a standard tape, it was pasted on the laminated surface of release paper, a 180' peel test was conducted in accordance with JIS-Z-0237, and further JIS-Z
-1523, the residual adhesion rate was measured.

(hereinafter abbreviated as PP) and melt index (hereinafter abbreviated as MI) are O67fi/l Omin
.

Low-density polyethylene (Showa Denko K.K. Nijiyo Rex) (hereinafter abbreviated as LD) with a density of 0.925 is PP/L.
A mixture melt-mixed in a ratio of D=80/20 (wt%) with a viscosity of 500 at 25°C was laminated on kraft paper with a resin temperature of 315°C and a lamination thickness of 10 μm, followed by extrusion lamination with an oxygen concentration of 300°C. ppm
After electron beam irradiation treatment was performed at a j-line speed of 30 m/rnin and an irradiation dose of 4 megarads, heat treatment was performed for 3 days at 80° C. in the roll form with the gear open. The results are shown in Table 1. Example 2 Co-extrusion laminate with polypropylene laminated in Example 1 [Resin temperature 315°C, laminate thickness 10 μm]
The same test as in Example 1 was conducted except for the following. The results are shown in Table 1.

Example 3 In Example 1, the mixing ratio of pp and LD was set to PP/LD=80/
20 (weight #%), PP/LD=70/30
The same procedure as in Example 1 was carried out except that the amount of (% by weight) was used. The results are shown in Table 1.

Example 4 In Example 1, the viscosity of PDMS-1 at 25°C was 3000C8 (hereinafter abbreviated as PDMS-If).
Example 1 was carried out in the same manner as in Example 1 except that dimethylpolysiloxane was used. The results are shown in Table 1.

Example 5 I did the same. The results are shown in Table 1.

Example 6 The same procedure as in Example 1 was carried out except that the amount of PDMS-1 added in Example 1 was changed to 5% by weight instead of 3% by weight. The results are shown in Table 1.

Example 7 In Example 1, the electron beam irradiation dose was changed to 2 megarads instead of 4 megarads.
The same procedure as in Example 1 was carried out except that megarad was used. The results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was conducted except that electron beam irradiation was not performed. The results are shown in Table 1.

Comparative Example 2 The same procedure as in Example 1 was conducted except that the heat treatment was not performed. The results are shown in Table 1.

Comparative Example 3 The same procedure as in Example 1 was conducted except that the amount of PDMS-1 added to the resin mixture was 0.2% by weight. The results are shown in Table 1.

Comparative Example 4 In Example 1, when the amount of PDMS-III added to the resin mixture was 35% by weight, it could not be extruded with an extruder when mixed with the resin mixture.

Above, Examples 1 to 7. The measurement results of peel strength and residual adhesiveness of Comparative Examples 1 to 3 are shown in the first example. In addition, as a reference example, the peel strength and residual adhesiveness of iron kraft tape used as a standard tape were measured in the same manner as in Example 1, and the results are also listed in Table 1.

Table 1 [Effects of the Invention] As described above, the method of the present invention achieves excellent peeling by mixing dimethylpolysiloxane with a 4-lyolefin thermoplastic resin, molding it, and subjecting it to electron beam irradiation treatment. It is possible to obtain a removable surface that can be written with marker ink instead of a smudge that exhibits high performance. Moreover, unlike conventional methods, large-scale equipment for heat treatment or solvent recovery is not required, and a releasable surface can be easily obtained, so the economic effect is extremely large.

Claims (8)

[Claims] (1) After molding a composition consisting of a polyolefin thermoplastic resin and dimethylpolysiloxane and allowing the dimethylpolysiloxane to bleed onto the surface of the molded product, electron beam irradiation is performed, and the polyolefin thermoplastic resin is further molded in air. 1. A method for producing a releasable material, which comprises performing heat treatment at a temperature below the melting point of the resin. (2) The amount of dimethylpolysiloxane in the composition is 0.5
The manufacturing method according to claim 1, wherein the content is 30% by weight. (3) The polyolefin thermoplastic resin is a mixture of two or more types of polyolefins, and the mixture contains polyethylene and a mono (or co)polymer of α-olefins C_3 to C_5 as essential components. The manufacturing method according to item 1. (4) The manufacturing method according to claim 1, wherein the irradiation dose of the electron beam is 20 megarads or less. (5) The manufacturing method according to claim 1, wherein the molded product is a film. (6) Claim 1 in which the molded product is a laminated film
Manufacturing method described in section. (7) The manufacturing method according to claim 6, wherein the laminated film has a three-layer structure of paper/polyolefin/dimethylpolysiloxane-containing polyolefin. (8) The manufacturing method according to claim 3, wherein the α-olefin of C_3 to C_5 is propylene.